In recent years, mobile devices have increasingly provided users with an elevated level of safety and security. In addition to being able to wirelessly contact another individual or service by dialing a number, mobile devices can be used as part of a Personal Emergency Response Systems (PERS). PERS devices and equipment are user-installed devices (wired or wireless) that may also attach to a landline network. The general concept is that the PERS user is able to provide location information for general monitoring and/or to alert an emergency response call center that they are in distress and need immediate assistance. Some PERS devices are capable of detecting events such as falls or extended periods of inactivity and alert the call center to these conditions. Regardless of the specific type of PERS device, the location of the mobile device is an important determination.
In modern mobile communication networks, the current position determination technologies use several methods of determining a subscriber's location before it defaults to the location of the serving sector. One such technology is Global Positioning System (GPS). GPS is a space-based satellite navigation system that provides location and time information anywhere on Earth, where there is an unobstructed line of sight to four or more GPS satellites. Standalone GPS operation uses radio signals from satellites alone. On the other hand, Assisted GPS (AGPS) additionally uses network resources to locate and use the satellites in poor signal conditions. For example, when signal conditions are poor (e.g., in a city or building), these signals may suffer multipath propagation where signals bounce off buildings, or may be weakened by passing through atmospheric conditions, walls, or tree cover. When a GPS location determination is attempted in these conditions, some standalone GPS navigation devices may not be able to fix a position due to the poor signal quality. A fix may take several minutes (if at all possible) rendering them unable to function effectively until a clearer signal can be received continuously for a long enough period of time. An assisted GPS system can address these problems by using data available from a network. For example, servers that include orbital information from satellites are used. A mobile device can contact such servers and download the information using a “secure user plane location” approach, which is an IP based protocol for AGPS to receive information of GPS satellites via IP.
Determining the location of a mobile device while the mobile device is in use is often problematic. For example, when a mobile device is indoors, both GPS and AGPS may fail to provide the location information because of a substantial degradation of the GPS satellite signals. Further, even if there are some GPS signals, a mobile device may not be able to be assisted in determining its location because the communication channel is preoccupied with voice communication. Put differently, some wireless technology, (e.g., CDMA) does not support simultaneous voice and IP data communication. Thus, the call would first have to be stopped in order for the mobile device to determine its location efficiently.
Accordingly, it would be beneficial to have a method and system that would be able to determine the location of a mobile device when GPS signals are not available to the mobile device. It would also be beneficial to have a method and system to determine the location of a mobile device while a mobile device is in use, without providing an impression to the user that an on-going call is severed. Similarly, it would be beneficial to use different location technologies that are best suited for different scenarios.